Gizi kurang pada balita ditandai dengan kondisi kurus, berat badan menurut panjang atau tinggi badan <-2 hingga -3 SD, serta lingkar lengan 11,5 – 12,5 cm pada anak usia 6-59 bulan. Data Puskesmas Sinorang tahun 2022 menunjukkan terdapat 40 balita dengan gizi kurang di wilayah kerjanya, dengan prevalensi 3,13% dari sepuluh desa di Kecamatan Batui Selatan. Penelitian ini bertujuan untuk mengetahui faktor-faktor penentu status gizi kurang pada balita di wilayah tersebut, menggunakan survei deskriptif dengan populasi 40 balita gizi kurang. Analisis data dilakukan dengan analisis univariat. Hasil penelitian menunjukkan bahwa pengetahuan ibu tentang gizi dalam kategori baik sebesar 47,5%, pendapatan keluarga kategori baik sebesar 2,5%, riwayat berat badan lahir (BBL) baik sebesar 62,5%, frekuensi makan baik sebesar 95,5%, kebiasaan porsi makan baik sebesar 27,5%, komposisi makanan baik sebesar 30%, status imunisasi dasar lengkap sebesar 37,5%, dan pemberian vitamin A lengkap sebesar 65%. Kesimpulan penelitian ini menunjukkan bahwa faktor utama gizi kurang pada balita adalah rendahnya pendapatan keluarga. Oleh karena itu, masyarakat, terutama orang tua balita, perlu berupaya memenuhi kebutuhan pangan keluarga dengan memaksimalkan potensi yang ada, seperti memanfaatkan pekarangan untuk tanaman pangan harian keluarga. Malnutrition in toddlers is characterized by a thin condition, weight according to length or height <-2 to -3 SD, and arm circumference of 11.5 – 12.5 cm in children aged 6-59 months. Data from the Sinorang Health Center in 2022 shows that there are 40 undernourished children under five in their work area, with a prevalence of 3.13% out of ten villages in South Batui District. This study aims to determine the determinants of malnutrition status in toddlers in the region, using a descriptive survey with a population of 40 undernourished toddlers. Data analysis was carried out by univariate analysis. The results showed that maternal knowledge about nutrition was in the good category of 47.5%, family income in the good category was 2.5%, birth weight history (BBL) was good at 62.5%, eating frequency was good at 95.5%, eating habits were good at 27.5%, food composition was good at 30%, complete basic immunization status was at 37.5%, and complete vitamin A was given at 65%. The conclusion of this study shows that the main factor of malnutrition in toddlers is low family income. Therefore, the community, especially parents of toddlers, need to strive to meet the family's food needs by maximizing the existing potential, such as utilizing the yard for the family's daily food crops.